The cloud point of petroleum products and biodiesel fuels is an index of the lowest temperature of their utility for certain applications. Wax crystals of sufficient quantity can plug filters used in some fuel systems.

Petroleum blending operations require a precise measurement of the cloud point.

This test method can determine the temperature of the test specimen at which wax crystals have formed sufficiently to be observed as a cloud with a resolution of 0.1°C.

This test method provides results that are equivalent to Test Method D 5773/IP 446. The temperature results of this test method have been found to be warmer than those of Test Method D 2500/IP 219 by an average of 0.49°C; however, no sample specific bias was observed.

Similar to Test Method D 5773/IP 446, this test method determines cloud point in a shorter period of time than Test Method D 2500/IP 219.

Note 1—In cases of samples with cloud points near ambient temperatures, time savings may not be realized.

Note 2—This test method eliminates most of the operator time required of Test Method D 2500/IP 219.

Note 3—The only utility required by the apparatus described in this test method is electricity with power consumption of approximately 20 watts. The electric power can come from an alternating current source (wall receptacle) or direct current source such as a battery or a cigarette lighter plug in a vehicle.

Note 4—The apparatus described by this test method can be made much smaller and lighter than that of Test Methods D 5773/IP 446 and D 2500/IP 219, allowing full portability.

Note 5—The apparatus used in the 2006 interlaboratory study weighed approximately 1 kg and occupied the space of a small lunch box. See Section 13.

1.1 This test method covers the determination of the cloud point of petroleum products and biodiesel fuels that are transparent in layers 40 mm in thickness by an automatic instrument.

1.2 This test method covers the range of temperatures from –60 to +20°C with temperature resolution of 0.1°C; however, the range of temperatures included in the 2006 interlaboratory cooperative test program only covered the temperature range of –35 to +12°C. See Section 13.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.